JPH04164858A - Sintered material of light rare earth oxide, production thereof and crucible comprising the same sintered material - Google Patents

Abstract

PURPOSE:To obtain a dense sintered material hardly collapsing, having excellent water resistance by sintering a compound of light rare earth element with a compound of a specific element to give an oxide. CONSTITUTION:(A) An oxide of a light rare earth element (selected from La, Ce, Pr and Nd) and (B) an oxide of element selected from Sc, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm Yb, Lu, Al, In, Tl, Ti, Zr, Hf, Si, Ge, Sn, Pb and Ni are used to give a sintered material of light rare earth element. The ratio of each composition of the component A:B is 99:1-50:50 in molar ratio of element. The sintered material is produced by molding a mixture of the raw material compound in a given ratio by using an ordinary monoaxial press and sintering at 1,000-1,900 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light rare earth oxide sintered body that is dense and has excellent water resistance, a method for producing the same, and a crucible using the same.

[Conventional technology]

In recent years, the development of new materials such as electronic/optical materials, semiconductor materials, magnetic materials, superconducting materials, and new ceramic materials has been actively carried out on a global scale.

In developing such new materials, it is extremely important to evaluate the essential physical properties of the materials, and such evaluations require highly pure materials. For example, analysis of single crystals can be considered as a clue to elucidating superconducting phenomena. Accurate analysis requires highly pure single crystals, but at present it is difficult to obtain high-quality single crystals. One of the causes is that constituent elements of a container such as a crucible used for single crystal synthesis mix into the single crystal, which is so-called contamination. To solve this problem, containers made of elements selected from among the constituent elements of superconductors are increasingly being used.

This situation is also occurring in the electronics and glass fields.

Containers used for this purpose include containers made of rare earth oxides, such as oxides of heavy rare earth elements such as IJum. Also, recently, lantern, cerium,
There has also been a demand for containers made of oxides of light rare earth elements such as praseodymium and neodymium.

[Problem to be solved by the invention]

However, light rare earth oxides have a property that other rare earth oxides do not have, that is, they easily react with moisture to form hydroxides, so their sintered bodies and containers using them cannot be manufactured in the short term. It has the disadvantage of collapsing in between.

[Means to solve the problem]

Therefore, the present inventors have conducted various studies to solve the above problems, and have found that if light rare earth compounds are sintered with compounds of specific elements, the sintered material will not disintegrate easily, will be dense, and will have excellent water resistance. We discovered that a sintered body can be obtained, and that by using a crucible using the sintered body, it is possible to produce new materials of high quality without contamination.
The invention has been completed.

That is, the present invention provides (a) an oxide of a light rare earth element selected from the group consisting of lanthanum, cerium, praseodymium, and neodymium, and (b) scandium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, and an oxide of an element selected from the group consisting of erbium, thulium, ytterpium, lutetium, aluminum, gadolinium, indium, thallium, titanium, zirconium, hafnium, silicon, germanium, tin, lead and nickel. The present invention provides a light rare earth oxide sintered body and a method for producing the same.

Furthermore, the present invention provides a crucible characterized in that at least the contact surface with the sample is made of the light rare earth oxide sintered body.

The light rare earth oxide sintered body of the present invention (hereinafter referred to as the sintered body of the present invention) is a compound of a light rare earth element selected from the group consisting of (A) lanthanum, cerium, praseodymium, and neodymium (hereinafter referred to as (A) ) and (B) candium, promethium, samarium, europium,
Compounds of elements selected from the group consisting of gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterpium, lutetium, aluminum, gadolinium, indium, thallium, titanium, zirconium, hafnium, silicon, germanium, tin, lead and nickel ( It can be produced by sintering a mixture with (hereinafter referred to as (B) compound).

Examples of the compound (8) used as a raw material include the above-mentioned oxides of light rare earth elements; hydrochlorides, sulfates, nitrates,
Examples include inorganic acid salts such as carbonates; organic acid salts such as citrates; hydroxides; alkoxides; one type of these compounds may be used, or two or more types may be used as a mixture. Also good. Further, the compound (B) is used as a sintering aid, and examples thereof include oxides of the above-mentioned elements; inorganic acid salts such as hydrochlorides, sulfates, nitrates, and carbonates; citrates, etc. Organic acid salts; hydroxides; alkoxides, etc. may be used, and one type of these compounds may be used, or two or more types may be used in combination. Here, alkoxide has excellent mixability when mixing raw materials, but
On the other hand, it is expensive, so it should be selected according to the purpose of use. Note that the raw material used in the present invention has a normal purity, that is, about 95 to 99%, which is sufficient depending on the use of the sintered body.

Sintering is performed by mixing these raw materials, molding, and then sintering according to a conventional method.

The mixing ratio of the raw materials is such that the ratio of the above-mentioned light rare earth elements contained in component (a) and the above-mentioned elements contained in component )
: Component (b) to 99 : 1 to 50 : 50 is preferable. If component (a) is more than 99 mol% and component (b) is less than 1 mol%, the effect of adding component (b), which is a sintering aid, is not sufficient and the light rare earth oxide in the sintered body is (Component (a)) absorbs water and becomes hydroxide, which causes the sintered body to collapse, which is undesirable.
If it is less than mol% and the component (etc.) exceeds 50 mol%,
This is not preferable because the components in the sintered body may be mixed into the material to be produced.

As the mixing method, any of a dry mixing method, a wet mixing method, and a coprecipitation method may be used. When using the dry mixing method, it is preferable to use an alumina or genzui mortar or a ball mill thereof. As the solvent in the wet mixing method, it is preferable to use an organic solvent with a relatively low boiling point, such as ethanol or acetone. It is not preferable to use water as a solvent because the component (B) to be added may dissolve. Further, it is not preferable to use an organic solvent with a high boiling point because it becomes difficult to separate the solvent and the mixed powder. Generally, when using the coprecipitation method,
Although a uniform mixed powder can be obtained, care must be taken as impurities from the precipitant used and large amounts of raw material ions remaining in the solution may cause weighing errors.

Next, the obtained mixed powder is shaped and sintered.

A normal uniaxial press can be used for molding. The temperature required for sintering is preferably in the range of 1000 to 1900°C.

If the temperature is less than 1000°C, sintering is not sufficient and a dense sintered body cannot be obtained, and if it exceeds 1900°C, the added component (B) may volatilize or the sintered body may melt. I don't like it because it is. In addition, for sintering, 5
If sintering is performed after calcination at 00 to 1200°C, the density of the resulting sintered body may be improved.

The thus obtained sintered body of the present invention is difficult to disintegrate, is dense, and has excellent water resistance. Therefore, if it is formed into a crucible shape and then sintered, the sintered body of the present invention having such properties can be obtained. A crucible is obtained.

The crucible of the present invention only needs to have at least the contact surface with the sample made of the sintered body of the present invention. Therefore, the crucible of the present invention can also be manufactured by forming a sprayed layer made of the sintered body of the present invention on a crucible-shaped structure having another composition by a thermal spraying method. Here, materials for the structure having other compositions include TaSMo, Ga, Nb, H
High melting point metals such as f and heat resistant materials such as carbon and silicon carbide can be used. The parameters for obtaining a high-quality sprayed layer are gas H2/N2, voltage 20-60V, and current 600V.
~1000^, and the raw material feed rate is preferably 20 to 60 g/min.

〔Effect of the invention〕

According to the present invention, a light rare earth oxide sintered body and a crucible that are dense and have excellent water resistance are obtained. By using the crucible of the present invention, high-quality new raw materials without contamination can be produced.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example 1 Lanthanum hydroxide with a purity of 99.9% and aluminum hydroxide were weighed so that the weight ratio in terms of oxide was 90:10 (element molar ratio La:^1 to 74:26),
Mixed by wet mixing method. The mixed raw materials were calcined at 1000°C for 5 hours, then molded and sintered at 1550°C for 10 hours. The obtained sintered body had a theoretical density of 99%. When this sintered body was left in a constant temperature and humidity room at 90% relative humidity and 30° C., the density of the sintered body after 30 days was the same as that at the time of sintering, and no change in appearance was found.

Example 2 Lanthanum hydroxide with a purity of 99.9% and titanium oxide were mixed in a weight ratio of 90:10 (elemental molar ratio of La
: Ti = 81 : 19) and mixed by a wet mixing method. The mixed raw materials were calcined at 1000°C for 5 hours, then molded and sintered at 1550°C for 10 hours. The obtained sintered body had a theoretical density of 99%. When this sintered body was left in a constant temperature and humidity room at 90% relative humidity and 30°C,
The density of the sintered body after one day was the same as that during sintering, and no change in appearance was found.

Example 3 Lanthanum hydroxide and thallium oxide with a purity of 99% were each weighed 3.0% in terms of oxide weight. Okg, 1. A slurry was prepared by adding 900 cc of distilled water, 35 g of ammonium polycarboxylate, and 78 g of acrylic acid emulsion to the raw material powder weighed so that the molar ratio of elements was 0 kg (element molar ratio a:TA' = 81:19). This slurry was poured into a mold and formed into a crucible shape, and then sintered at 1500° C. for 20 hours to obtain a crucible. Note that the density of the sintered body was 99% of the theoretical density.

Into this crucible, lanthanum oxide, strontium carbonate, and copper oxide were weighed to give La+, essro, I5CUO4, and copper oxide was added three times the weight as a fluxing agent.The mixed raw materials were melted at 1100°C for 2 hours. 0
．． It was cooled to 900° C. at a cooling rate of 1 t/min, and then lowered at a rate of 3° C./min to obtain the desired single crystal. fluorescence xi
As a result of the analysis, there was no contamination of elements other than the raw materials in this sample.

Example 4 Lanthanum oxide with a purity of 99% and europium oxide were mixed in a ratio of 88:12 in terms of oxide weight (Element molar ratio: La:
Bu=89:11) and mixed. T
A plasma sprayed film with a thickness of 1 mm was formed in a heat-resistant crucible manufactured by A, under conditions of a voltage of 82 V and a current of 850^.

Using this crucible, Lad, escao, +5cL
When a single crystal of I04 was produced under the same conditions as in Example 3, there was no contamination at all.

Example 5 Cerium oxide and aluminum oxide with a purity of 99% were 88 + 12 in terms of oxide weight (Ce:^ in elemental molar ratio)
1=68:32) and mixed. T
A plasma sprayed film with a thickness of 1 mm was formed in a heat-resistant crucible made by Al& under conditions of a voltage of 82 M and a current of 850^.

Using this crucible, siaa1, escao, +s[,
When a uOn single crystal was produced under the same conditions as in Example 3, there was no contamination at all.

Example 6 99% pure Brasinazodium oxide and tin oxide were weighed to give a weight of 3.0 kg and 0.6 kg (element molar ratio: Pr:Sn=80:20), respectively, in terms of oxide weight. , 900 cc of distilled water, 36 g of ammonium polycarboxylate, and 79 g of acrylic acid emulsion were added and mixed to prepare a slurry. After pouring this slurry into a mold and forming it into a crucible shape, it was heated to 1500℃ for 20 minutes.
A crucible was obtained by time sintering. Note that the density of the sintered body was 99% of the theoretical density.

Lad, essro, 15CU using this crucible
When a single crystal of Os was produced under the same conditions as in Example 3, there was no contamination at all.

Example 7 Lanthanum oxide with a purity of 99% and titanium oxide were mixed in a ratio of 80:20 (element molar ratio: La:Ti) in terms of oxide weight.
= 66:34) and mixed. A plasma sprayed film with a thickness of 1 mm was formed on a heat-resistant crucible made of Ta under the conditions of a voltage of 82 v and a current of 850^.

Using this crucible, Lad, 5scao, +5Cu
When a single crystal of O< was produced under the same conditions as in Example 3, there was no contamination at all.

Comparative Example 1 A sintered body of 99% pure lanthanum oxide was prepared in the same manner as in Example 1. This sintered body disintegrated in air for 5 hours. This was understood to be due to the conversion of lanthanum oxide to lanthanum hydroxide.

that's all Applicant: Onoda Cement Co., Ltd.

Claims (4)

[Claims] 1. (a) an oxide of a light rare earth element selected from the group consisting of lanthanum, cerium, praseodymium and neodymium; (b) scandium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterpium; and an oxide of an element selected from the group consisting of lutetium, aluminum, gadolinium, indium, thallium, titanium, zirconium, hafnium, silicon, germanium, tin, lead and nickel. Body. 2. The light rare earth oxide sintered body according to claim 1, wherein the ratio of component (a) to component (b) is 99:1 to 50:50 in elemental molar ratio. 3. (A) a compound of a light rare earth element selected from the group consisting of lanthanum, cerium, praseodymium, and neodymium; and (B) scandium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterpium, and lutetium. , and a compound of an element selected from the group consisting of aluminum, gadolinium, indium, thallium, titanium, zirconium, hafnium, silicon, germanium, tin, lead and nickel. A method for producing a rare earth oxide sintered body. 4. A crucible in which at least a surface in contact with a sample is made of the light rare earth oxide sintered body according to claim 1.